The long-term objectives of this proposal are (1) to investigate the dynamicsand physiology of T-even phage replication under conditions relevant to the natural environment and to potential therapeutic applications, i. e. during anaerobic respirative and fermentative growth of the host, (2) to identify and characterize T-even phages capable of infecting E. coil 0157:147 anaerobically and use appropriately-designed mixed-culture fermenters to assess the potential for use of these phages as a means of reducing the 0157:147 load in the guts of cattle, and (3) t'dentify regimes for efficiently producing and effectively administering the chosen phages. Preliminary experiments have identified 12 T-even phages that can infect 0157 and have shown that some T-even phages can infect E. coli growing under conditions of anaerobic respiration and/or fermentation, but the process is substantially different than during aerobic infection, and also differs between fermentation and respiration, between different host strains and between different related phages. Studies will include effects of available nutrients, electron acceptors, and pH and will determine various phage growth parameters --adsorption efficiency, lysis time and lysis inhibition patterns, intracellular phage production, and burst size. This data will be used to set up continuous-flow anaerobic fermentors simulating the bovine rumen and the colon environment to model in the laboratory the population dynamics of the relationship between predator (phage) and prey (including nonpathogenic derivatives of E. coli 0157:147), facilitating selection of the most promising phages and diets for treatment and exploration of the parameters of phage-host interaction as they are affected by conditions and by the presence of other rumen and colon bacteria. Phage will be prepared and supplied to Dr. Todd Callaway of the USDA, who will extend these studies to pathogenic strains and to in vivo studies in cattle. Such experiments are very well suited to work by students in our undergraduate setting, leading to a firm foundation in understanding microbial ecology and physiology, general microbial and anaerobic techniques, proteomics, and experimental design, along with the satisfaction of contributing significant new research results.